In transformers, two or more multi-turn coils of conducting material are arranged so that any magnetic flux linking one coil will link the other coils, also. The mutual inductance existing between the coils transfers energy from one input coil, or primary winding, to the other coils, or secondary windings.
When a high current is supplied to the transformer, the coils are urged to attain a spherical shape and tend to fly apart, both radially and axially. It is known that, by gluing the coils to a core or binding the coils with material such as an insulative wrapping paper, it is possible to minimize the tendency of the coils to fly apart. It is, however, desirable to further minimize production steps in transformer manufacturing.
It is generally necessary to insulate successive turns of the coil from one another and to insulate concentric coils from one another to prevent shorting. To this end, it is common to form coils from conductors having a thin insulative coating in the form of a thin film or a nylon mesh. The insulative coating must, however, be removed from the conductor at weld and termination points. Moreover, shorting may occur where the thin insulative coating is abraded, such as when core steel is provided in an opening defined by an inner coil. Typically, protective material such as pressboard is provided at various points around such an opening to prevent damage to the insulation of the coil. It is desirable to avoid the need for insulative coatings and protective material in a transformer.
Beside providing insulative coatings on the conductors forming the coils, primary and secondary coils may be insulated from each another as shown, for example, in U.S. Pat. No. 1,558,090, which teaches cutting a spiral groove in an insulative cylindrical supporting member and forming a primary coil by winding bare wire around the member in the groove. A secondary coil is formed around the member and is prevented from contacting the primary coil either through the use of a conductor too large to be received in the groove, by filling the groove with insulating material prior to winding the conductor, or by winding the conductor so that the turns of the secondary coil do not enter the grooves. U.S. Pat. No. 2,205,236 teaches forming a core or supporting member and positioning a molded insulative spiral having an interior diameter equal to the exterior diameter of the core around the core to insulate successive turns of the winding. The foregoing techniques suffer disadvantages including requiring substantial processing of the insulative member or members prior to winding the conductors.
U.S. Pat. No. 3,046,509 teaches forming a coil by winding a conductor around a mandrel together with a split flexible insulating flange having an L-shape, wherein one of the legs of the L-shaped flange extends radially between adjacent turns of the coil to separate them from one another. A pair of plates are arranged at opposite ends of the coils to hold the conductors and insulating material tightly together.
It is desirable to provide a turn-to-turn insulating member that requires minimal processing. It is further desirable to provide a means for simplifying the formation of insulated coil turns.